Preparation methods and applications of bio-based isomeric dodecane

Abstract

This invention proposes a method for preparing bio-based isomeric dodecane and its application, belonging to the field of organic chemical engineering. The method for preparing bio-based isomeric dodecane includes the following steps: Biomass jet fuel is fed into a vacuum distillation column for vacuum distillation; the distillation product is collected from the bottom side stream of the column, and the concentration of the C12 fraction in the product is ≥92%; the product is added to a flash distillation column to remove residual light components, reducing the content of light component impurities to ≤0.8%; the flash product is added to a molecular distillation apparatus for distillation under a vacuum of <1 Pa, obtaining a crude product with a purity greater than 98.5%; the crude product is then subjected to adsorption treatment in an activated carbon-molecular sieve composite bed to obtain cosmetic-grade bio-based isomeric dodecane. This method has the advantages of low energy consumption and high selectivity, and the prepared bio-based isomeric dodecane meets cosmetic standards and can be used in the manufacture of cosmetics.

Description

Technical Field

[0001] This invention belongs to the field of organic chemical technology, and in particular relates to a method for preparing and applying bio-based isomeric dodecane. Background Technology

[0002] Iso-dodecanes are widely used in high-end skincare and makeup products as solvents, emollients, or carriers due to their low irritation, high volatility, and excellent skin-feel adjustment capabilities. They are suitable for products requiring rapid evaporation and residue-free application, such as makeup removers and sunscreens. However, traditional iso-dodecane production relies primarily on petroleum-based feedstocks, resulting in high carbon emissions, non-renewable feedstocks, and the risk of allergic reactions from residual impurities such as aromatics and sulfides. Furthermore, the odor of the products may not meet cosmetic industry standards.

[0003] Biomass jet fuel, a low-carbon fuel derived from renewable resources, is rich in C10-C16 isoalkanes, making it a key alternative to petroleum-based feedstocks for the preparation of isododecanes. However, because biomass jet fuel is prepared through Fischer-Tropsch synthesis or hydrodeoxygenation processes, its composition is complex. Oxygen-containing compounds such as esters, aldehydes, and ketones, as well as short-chain impurities, in biomass jet fuel easily produce irritating odors. The isoalkanes obtained by direct separation often contain odorous substances, which do not meet the odorless requirements for cosmetics. Furthermore, traditional distillation processes require multiple fractionation or hydrorefining, resulting in high energy consumption and damage to the molecular structure, with the purity of the obtained product being less than 95%, making it suitable for industrial-grade products.

[0004] Therefore, there is an urgent need to develop a green, efficient, and low-energy-consumption preparation process for producing cosmetic-grade isomeric dodecane from biomass jet fuel. Summary of the Invention

[0005] This invention addresses the technical problems of existing technologies for preparing isomeric dodecanes using petroleum-based raw materials, which are not environmentally friendly, have low product purity, and high energy consumption. It also addresses the issues of low product purity, strong odor, and high energy consumption resulting from direct distillation of biomass jet fuel, both of which fail to meet cosmetic industry standards. The invention proposes a low-energy, highly selective method for preparing isomeric dodecanes. The resulting bio-based isomeric dodecanes meet the stringent safety, odor, and stability requirements of the cosmetic industry.

[0006] To achieve the above objectives, the technical solution adopted by this invention is as follows: a method for preparing bio-based isomeric dodecane, comprising the following steps: feeding biomass jet fuel into a vacuum distillation column for vacuum distillation, wherein the concentration of C12 fraction in the distillation product collected from the bottom side stream of the vacuum distillation column is ≥92%; adding the distillation product to a flash distillation column to remove residual light components, reducing the content of light component impurities to ≤0.8%; adding the flash distillation product to a molecular distillation apparatus for distillation under a vacuum of ≤1Pa, wherein the purity of the crude product obtained is >98.5%; and subjecting the crude product to adsorption treatment in an activated carbon-molecular sieve composite bed to obtain cosmetic-grade bio-based isomeric dodecane.

[0007] In one embodiment, vacuum distillation specifically includes the following steps: distillation is carried out under an absolute pressure of 5-20 kPa, and the fraction with a boiling range of 210-240℃ is collected to obtain an enriched fraction mainly composed of C12 isoalkanes. The technical solution of this invention removes a large number of components that differ significantly from the target product through distillation.

[0008] In one embodiment, an inert gas is introduced during vacuum distillation, with a flow rate of 0.5-2 vol% of the biomass jet fuel feedstock. This invention reduces the risk of decomposition of heat-sensitive components by introducing an inert gas during vacuum distillation.

[0009] It is understood that, based on actual circumstances, those skilled in the art can adjust the flow rate of the inert gas within the above range. For example, the flow rate of the inert gas can also be any point value within the range of 0.5 vol%, 0.6 vol%, 0.7 vol%, 0.8 vol%, 0.9 vol%, 1.0 vol%, 1.1 vol%, 1.2 vol%, 1.3 vol%, 1.4 vol%, 1.5 vol%, 1.6 vol%, 1.7 vol%, 1.8 vol%, 1.9 vol%, 2.0 vol%.

[0010] In one embodiment, during the reduced pressure distillation step, the theoretical number of trays is 50-70, the reflux ratio is 7-10:1, the feed is taken from the 30th-40th tray in the middle, the pressure at the top of the column is controlled at 5-15 kPa, and the temperature at the top of the column is 80-120°C.

[0011] In one embodiment, the operating conditions for adding the distillation product to a flash distillation column to remove residual light components are as follows: operating pressure of 5-10 kPa, temperature of 70-90°C, and residence time of 15-25 s. Under these conditions, the flash distillation method of this invention can rapidly remove low-boiling-point impurities such as C11 isoalkanes, preventing them from azeotropically reacting with the target components during molecular distillation, reducing the load on subsequent molecular distillation, and simultaneously lowering distillation costs.

[0012] In one embodiment, the flash distillation product is added to a molecular distillation apparatus for distillation under a vacuum of ≤1 Pa. The operating conditions are as follows: molecular distillation vacuum ≤1 Pa, evaporation temperature 60-100℃, and condensation surface temperature ≤20℃. Under a high vacuum environment of ≤1 Pa, the differences in the molecular path of free motion of isododecane (0.18 μm), isotridecane (0.15 μm), and n-dodecane (0.12 μm) are amplified by 3-5 times, thereby improving the enrichment efficiency of C12 and achieving a crude product purity of over 98.5%.

[0013] It is understood that, depending on the actual situation, those skilled in the art can adjust the molecular distillation vacuum degree and evaporation temperature within the above range. For example, the molecular distillation vacuum degree can also be 0.1 Pa, 0.2 Pa, 0.3 Pa, 0.4 Pa, 0.5 Pa, 0.6 Pa, 0.7 Pa, 0.8 Pa, 0.9 Pa, 1.0 Pa or any value within the above range, and the evaporation temperature can also be 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃ or any value within the above range.

[0014] In one embodiment, the crude product is adsorbed through an activated carbon-molecular sieve composite bed. The specific steps include: pretreating activated carbon and molecular sieve separately, preparing an activated carbon-molecular sieve composite bed with a mass ratio of activated carbon to molecular sieve of 1:1-3:1, and then adsorbing the crude product through the bed for 1-3 hours at an adsorption temperature of 80-120℃. This invention utilizes activated carbon to adsorb large molecular pigments and oxygen-containing compounds, while molecular sieves selectively remove small molecular aldehydes and ketones, resulting in a target product that meets cosmetic standards.

[0015] In one embodiment, the pretreatment step for activated carbon is: activating the activated carbon at 350°C for 2-6 hours under a nitrogen atmosphere; the pretreatment step for molecular sieve is: baking the molecular sieve at 350°C for 3 hours to remove moisture.

[0016] In one embodiment, the activated carbon has a particle size of 1-3 mm and a specific surface area ≥1000 m². 2 / g, pore volume 0.8-1.2cm 3 / g, the activated carbon is coconut shell-based or wood-based activated carbon; the molecular sieve has a particle size of 2-4mm and a specific surface area ≥500m². 2 / g, pore volume 0.3-0.5cm 3 / g, the molecular sieve used is 3A type molecular sieve or 5A type molecular sieve.

[0017] In another aspect, the present invention provides the application of the bio-based isomeric dodecane obtained by the above preparation method in cosmetic manufacturing.

[0018] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0019] This invention utilizes biomass jet fuel as raw material throughout the entire preparation process, without any chemical additives, reducing the carbon footprint by 40%. The final product meets the cosmetic natural source index standard (ISO 16128), with a natural source index of 0.6-0.7, achieving the triple goals of "high purity, zero odor, and low carbonization." First, the biomass jet fuel is fed into a vacuum distillation column, employing vacuum operation and structured packing to enrich C12 isoalkanes to over 92%, ensuring the purity of isododecane and avoiding high-temperature cracking. Then, pre-flash evaporation removes light components, reducing the load on subsequent molecular distillation while simultaneously deoxygenating to ensure oxidative stability. Next, molecular distillation, under low temperature and high vacuum, further increases the purity to over 98.5%, reducing energy consumption by 30%. Finally, adsorption is achieved through an activated carbon-molecular sieve composite bed, where activated carbon retains large molecular esters and molecular sieves separate small molecular aldehydes and ketones, resulting in a total odor substance content of <10 ppm, meeting cosmetic standards. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of the method for preparing bio-based isomeric dodecane provided in an embodiment of the present invention;

[0021] Figure 2 The GC-MS spectrum of the bio-based isomeric dodecane prepared in Example 1 of this invention;

[0022] Figure 3 This is the GC-IMS spectrum of Embodiment 1 of the present invention;

[0023] Figure 4 This is the GC-IMS spectrum of Comparative Example 1 of the present invention.

[0024] In the attached diagram, 1 is a distillation column; 2 is a flash distillation column; 3 is a molecular distillation apparatus; and 4 is an adsorption column. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] This invention provides a method for preparing bio-based isomeric dodecane and its application. The method for preparing bio-based isomeric dodecane uses biomass jet fuel as raw material, contains no chemical additives, and the final product meets the natural index standards for cosmetics. The specific steps employ a particular sequential process of distillation-flash evaporation-molecular distillation-adsorption, which can solve the problems of impurity removal, purification, and deodorization step by step, avoiding rework and resulting in low energy consumption.

[0027] The method for preparing bio-based isomeric dodecane of the present invention includes the following steps:

[0028] Distillation and Cutting: Biomass jet fuel feedstock is fed into vacuum distillation column 1 and distilled under an absolute pressure of 5-20 kPa. The fraction with a boiling range of 210-240℃ is collected to obtain an enriched fraction mainly composed of C12 isoalkanes, which is the distillation product. The concentration of C12 fraction in the distillation product is ≥92% when it is collected from the side stream. During the distillation process, an inert gas is introduced at a flow rate of 0.5-2 vol% of the biomass jet fuel feedstock to reduce the risk of decomposition of heat-sensitive components. Preferably, the inert gas is nitrogen or argon.

[0029] Pre-flash evaporation: The distillation product is added to flash column 2, with the operating pressure set to 5-10 kPa, the temperature set to 70-90℃, and the residence time set to 15-25 s. This rapidly removes low-boiling-point impurities such as C11 isoalkanes, preventing them from azeotropically reacting with the target component during molecular distillation, while also reducing distillation costs. After pre-flash evaporation, the content of light impurities in the mixture is reduced to ≤0.8%.

[0030] Molecular distillation: The pre-flash-treated mixture is added to a molecular distillation apparatus 3. The molecular distillation vacuum is set to ≤1 Pa, preferably 0.1-1 Pa. The evaporation temperature is set to 60-100℃, the condensation surface temperature is ≤20℃, the forced heat transfer condition is 300 rpm, and the liquid nitrogen condensation condition is -40℃. Since the molecular path of isododecane (0.18 μm) is greater than that of isotridecane (0.15 μm), and the molecular path of isododecane (0.18 μm) is greater than that of n-dodecane (0.12 μm), under a high vacuum environment of ≤1 Pa, the difference in the path of freedom is amplified by 3-5 times, which improves the enrichment efficiency of C12 and the purity of the crude product reaches more than 98.5%.

[0031] Activated carbon-molecular sieve composite adsorption: The crude product treated by molecular distillation is adsorbed in adsorption tower 4 using activated carbon-molecular sieve composite adsorption. The activated carbon and molecular sieve are pretreated separately, and then mixed at a mass ratio of 1:1 to 3:1 to prepare a composite bed. The residence time is 1-3 hours, and the adsorption temperature is set at 80-120℃ to improve the adsorption rate. The pretreatment steps for activated carbon are: activating the activated carbon at 350℃ for 2-6 hours under a nitrogen atmosphere; and the pretreatment steps for molecular sieve are: baking the molecular sieve at 350℃ for 3 hours to remove moisture. The activated carbon is coconut shell-based or wood-based activated carbon with a particle size of 1-3 mm, preferably 1.5-2 mm, and a specific surface area ≥1000 m². 2 / g, pore volume 0.8-1.2cm 3 / g; The molecular sieve used is type 3A or type 5A molecular sieve, with a particle size of 2-4mm, preferably 3mm, and a specific surface area ≥500m². 2 / g, pore volume 0.3-0.5cm 3 / g.

[0032] In the preparation method described above, the entire process uses biomass jet fuel as raw material, without any chemical additives. The final product meets the cosmetic naturalness index standard (ISO 16128), with a naturalness index of 0.6-0.7, achieving the triple goals of "high purity, zero odor, and low carbonization." First, a preliminary separation of the mixture is performed through distillation, using reduced pressure and structured packing to remove a large number of components significantly different from the target product, enriching C12 isoalkanes to over 92% and avoiding high-temperature cracking. Then, flash evaporation further removes light impurities, reducing the load on subsequent molecular distillation while simultaneously deoxygenating to ensure oxidative stability. Next, precise molecular-level separation is achieved through molecular distillation, and finally, deep adsorption removes impurities. This sequential process, from coarse to fine, gradually improves product purity and efficiently achieves the separation target. Simultaneously, each step creates more favorable conditions for subsequent steps, allowing each step to fully exert its separation effect, improving the overall process efficiency, and shortening the production cycle. Distillation and flash evaporation remove most of the impurities, reducing the amount of impurities entering the molecular distillation equipment and lowering the risk of equipment contamination and wear. At the same time, they also prevent a large number of impurities from occupying the adsorption sites of the adsorbent, extending the service life of the adsorbent and reducing production costs.

[0033] The preparation method of this invention involves first refining biomass jet fuel under reduced pressure. A high theoretical plate number and high reflux ratio distillation column 1 is used to cut a narrow fraction at 215-235℃, ensuring the purity of isododecane. In this refining step, the theoretical plate number, reflux ratio, and feed location are optimized to enrich light components at the top and heavy components at the bottom, controlling the purity of the crude product to be higher than 92%. The theoretical plate number is 50-70, the reflux ratio is 7-10:1, and the feed is from the 30th-40th plate in the middle section. The top pressure is controlled at 5-15 kPa, and the top temperature is 80-100℃. The fraction is then added to a flash distillation column 2 to remove light components, reducing the load on subsequent molecular distillation. Utilizing the difference in vapor pressure between C10-C11 isoalkanes and C12 alkanes, residual light components are removed, reducing the light impurity content to ≤0.8%. A molecular distillation apparatus 3 is used, with conditions set at 300°C. Forced heat transfer via scraped film at rpm, combined with liquid nitrogen condensation at -40℃, separates isomeric dodecane with a purity ≥98.5%. The scraped film heat transfer forms an extremely thin liquid film, increasing the heat transfer area and enabling efficient, uniform, and gentle evaporation. Liquid nitrogen condensation provides an ultra-low temperature cold trap, instantly, efficiently, and thoroughly capturing escaped vapor molecules, maintaining a high vacuum in the system, and preventing backmixing and cross-contamination. Finally, the fraction is adsorbed through an activated carbon-molecular sieve composite bed. Activated carbon adsorbs large-molecule pigments and oxygen-containing compounds with a decolorization rate ≥98%, while the molecular sieve selectively removes small-molecule aldehydes and ketones with a removal rate >95%, resulting in a total odor substance content <10ppm, ultimately yielding a target product that meets cosmetic standards.

[0034] To more clearly and in detail introduce the preparation method and application of bio-based isomeric dodecane provided in the embodiments of the present invention, the following description will be based on specific embodiments.

[0035] The composition of the biomass jet fuel used in the embodiments and comparative examples of this invention is shown in Table 1 below:

[0036] Table 1. Composition of Biomass Aviation Fuel Feed Fractions

[0037]

[0038] Example 1

[0039] 1.0L of biomass jet fuel is fed into vacuum distillation column 1. The fraction with a boiling range of 210-235℃ is cut at 15kPa to obtain the distillation product. This product is then added to flash distillation column 2, where the operating pressure is set to 8kPa and the temperature to 90℃ to remove 3-5% of the light components, yielding a mixture of heavy components. This mixture is then added to molecular distillation apparatus 3, where the vacuum degree is set to 0.5Pa, the evaporation temperature to 80℃, the forced heat transfer condition to 300rpm, and the liquid nitrogen condensation condition to -40℃, yielding a crude product. This crude product is then passed through a composite bed of coconut shell-based activated carbon and 5A molecular sieve at a mass ratio of 2:1, with the coconut shell-based activated carbon at the bottom and the 5A molecular sieve at the top, separated by a stainless steel mesh. The packing density is 0.45g / cm³ of activated carbon. 3 Molecular sieve 0.6 g / cm 3 The mixture was treated at 100°C for 2 hours to obtain isomeric dodecane with a purity of 98.7% and no off-odor.

[0040] Example 2

[0041] 1.0L of biomass jet fuel is fed into vacuum distillation column 1. The fraction with a boiling range of 210-235℃ is cut at 5kPa to obtain the distillation product. The distillation product is then added to flash distillation column 2, where the operating pressure is set to 8kPa and the temperature to 80℃ to remove 3-5% of the light components, yielding a mixture of heavy components. This mixture is then added to molecular distillation apparatus 3, where the molecular distillation vacuum is set to 0.5Pa, the evaporation temperature to 80℃, the forced heat transfer condition is 300rpm, and the liquid nitrogen condensation condition is -40℃, yielding a crude product. The crude product is then passed through a composite bed of coconut shell-based activated carbon and 5A molecular sieve at a mass ratio of 3:1, with the coconut shell-based activated carbon at the bottom and the 5A molecular sieve at the top, separated by a stainless steel mesh. The packing density is 0.45g / cm³ of activated carbon. 3 Molecular sieve 0.6 g / cm 3 The mixture was treated at 100°C for 3 hours to obtain isomeric dodecane with a purity of 98.8% and no off-odor.

[0042] Example 3

[0043] 1.0L of biomass jet fuel is fed into vacuum distillation column 1. The fraction with a boiling range of 210-235℃ is cut at 5kPa to obtain the distillation product. This product is then added to flash distillation column 2, where the operating pressure is set to 8kPa and the temperature to 90℃ to remove 3-5% of the light components, yielding a mixture of heavy components. This mixture is then added to molecular distillation apparatus 3, where the vacuum degree is set to 0.5Pa, the evaporation temperature to 80℃, the forced heat transfer condition to 300 rpm, and the liquid nitrogen condensation condition to -40℃, yielding a crude product. This crude product is then passed through a composite bed of coconut shell-based activated carbon and 5A molecular sieve at a mass ratio of 1:1, with the coconut shell-based activated carbon at the bottom and the 5A molecular sieve at the top, separated by a stainless steel mesh. The packing density is 0.45g / cm³ of activated carbon. 3 Molecular sieve 0.6 g / cm 3 The mixture was treated at 100°C for 3 hours to obtain isomeric dodecane with a purity of 98.8% and no off-odor.

[0044] Comparative Example 1

[0045] 1.0L of biomass jet fuel was fed into vacuum distillation column 1, where the fraction with a boiling range of 210-235℃ was cut at 15kPa to obtain the distillation product. The distillation product was then added to flash distillation column 2, where the operating pressure was set to 8kPa and the temperature to 170℃ to remove 3-5% of the light components, resulting in a mixture of heavy components. The mixture of heavy components was then added to molecular distillation apparatus 3, where the molecular distillation vacuum was set to 0.5Pa, the evaporation temperature to 80℃, and the rotation speed to 300rpm, to obtain isomeric dodecane with a purity of 98.8%. However, GC-IMS analysis showed an increase in off-odor substances in the product.

[0046] Comparative Example 2

[0047] 1.0L of biomass jet fuel is fed into vacuum distillation column 1. The fraction with a boiling range of 210-235℃ is cut at 5kPa to obtain the distillation product. The distillation product is then added to flash distillation column 2, where the operating pressure is set to 8kPa and the temperature to 170℃ to remove 3% of the light components, yielding a mixture of heavy components. The crude product is then passed through a composite bed of coconut shell-based activated carbon and 5A molecular sieve in a 1:1 mass ratio, with the coconut shell-based activated carbon at the bottom and the 5A molecular sieve at the top, separated by a stainless steel mesh. The packing density is 0.45g / cm³ of activated carbon. 3 Molecular sieve 0.6 g / cm 3 The mixture was treated at 100℃ for 3 hours to obtain isomeric dodecane with a purity of 97.8%. GC-IMS analysis showed an increase in the content of off-odor substances, with ketones exceeding 10 ppm and a distinct solvent odor.

[0048] Actual separation effect verification

[0049] The separation effect of Example 1 is shown in Table 2.

[0050] Table 2 Separation effect table of Example 1

[0051]

[0052] As can be seen from the above, the separation process of the present invention, consisting of distillation-flash evaporation-molecular distillation-adsorption steps, gradually improves the purity of the product by refining the separation process from coarse to fine, and can efficiently achieve the separation target. The final content of isomeric undecane in the obtained product is <0.1%, the final content of isomeric tridecane is 0.2%, and the content of isomeric dodecane is 98.7%, indicating that the purity of isomeric dodecane in the obtained product is high.

[0053] The isomeric dodecane prepared in Example 1 was analyzed by GC-MS, and the product spectrum is shown below. Figure 2 As shown in Table 3, the product composition analysis is presented in the table below.

[0054] Table 3. Compositional Analysis of the Isomeric Dodecane Product Prepared in Example 1

[0055]

[0056] As shown in Table 2, the peak area of ​​isododecane in the product obtained in Example 1 accounted for 98.7%, with a retention time of 11.12-14.88 min; the peak area of ​​normal dodecane accounted for 1.1%, with a retention time of 15.05 min; and the peak area of ​​isotridecane accounted for 0.2%, with a retention time of 15.12 min. The main component of the product obtained in Example 1 was isododecane, with a purity of 98.7%, a ketone content of only 1.3 ppm, and an alcohol content of only 2.5 ppm. Sensory evaluation by professionals showed no off-odor, indicating that the isododecane obtained in Example 1 can be used in the manufacture of cosmetics in the daily chemical industry.

[0057] Volatile component analysis

[0058] The volatile components of the products obtained in Example 1 and Comparative Example 1 were analyzed separately. The GC-IMS spectrum of Example 1 is attached. Figure 3 As shown in the attached figure, the GC-IMS spectrum of Comparative Example 1 is as follows. Figure 4 As shown, the background color is blue, and yellow to red represent a gradual increase in the content of volatile components. Figure 3 and Figure 4 It can be seen that the volatile components are mainly ketones and alcohols, and the changes before and after adsorption are significant, which shows the necessity of the adsorption process.

[0059] As can be seen from the above, the isomeric dodecanes obtained in Examples 1-3 of this invention all have a purity greater than 98.5% and are odorless. Comparative Example 1, without activated carbon-molecular sieve composite adsorption treatment, yielded isomeric dodecanes with a purity greater than 98.5%, but GC-IMS analysis showed an increase in odorous substances, failing to meet cosmetic manufacturing standards. Comparative Example 2, without molecular distillation treatment, yielded a product with a purity of only 97.8%, and an increased odorous substance, producing a noticeable solvent smell, also failing to meet cosmetic manufacturing standards. This demonstrates that each step in this invention is essential for preparing high-purity, odorless bio-based isomeric dodecanes. Each step provides more favorable conditions for the subsequent step, improving the overall separation efficiency of the process, ultimately resulting in high-purity, odorless bio-based isomeric dodecanes.

[0060] The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, alterations, evolutions, or improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing bio-based isomeric dodecane, characterized in that, Includes the following steps: Biomass jet fuel is fed into a vacuum distillation column for vacuum distillation under an absolute pressure of 5-20 kPa. The fraction with a boiling range of 210-240℃ is collected from the bottom side stream of the column, and the distillation product is obtained. The concentration of C12 fraction in the distillation product is ≥92%. The distillation product is then added to a flash distillation column, with an operating pressure of 5-10 kPa, a temperature of 70-90℃, and a residence time of 15-25 s to remove residual light components, reducing the impurity content of light components to ≤0.8%. The flash product is then added to a molecular distillation apparatus for distillation under a vacuum of ≤1 Pa, an evaporation temperature of 60-100℃, and a condensation surface temperature of ≤20℃ to obtain a crude product with a purity >98.5%. The crude product is then adsorbed onto an activated carbon-molecular sieve composite bed with a mass ratio of activated carbon to molecular sieve of 1:1-3:1 for a residence time of 1-3 h and an adsorption temperature of 80-120℃ to obtain cosmetic-grade bio-based isomeric dodecane.

2. The method for preparing bio-based isomeric dodecane according to claim 1, characterized in that, An inert gas is introduced during the vacuum distillation process, with a flow rate of 0.5-2 vol of the biomass jet fuel feed.

3. The method for preparing bio-based isomeric dodecane according to claim 1, characterized in that, In the vacuum distillation step, the theoretical number of trays is 50-70, the reflux ratio is 7-10:1, the feed is taken from the 30th-40th tray in the middle, the pressure at the top of the column is controlled at 5-15 kPa, and the temperature at the top of the column is 80-120℃.

4. The method for preparing bio-based isomeric dodecane according to claim 1, characterized in that, The adsorption treatment step also includes a pretreatment step for activated carbon and molecular sieve, respectively. The pretreatment step for activated carbon is to activate activated carbon at 350°C for 2-6 hours under a nitrogen atmosphere; the pretreatment step for molecular sieve is to bake molecular sieve at 350°C for 3 hours to remove moisture.

5. The method for preparing bio-based isomeric dodecane according to claim 1, characterized in that, The activated carbon has a particle size of 1-3 mm and a specific surface area ≥1000 m². 2 / g, pore volume 0.8-1.2cm 3 / g, the activated carbon is coconut shell-based or wood-based activated carbon; the molecular sieve has a particle size of 2-4mm and a specific surface area ≥500m². 2 / g, pore volume 0.3-0.5cm 3 / g, the molecular sieve used is 3A type molecular sieve or 5A type molecular sieve.

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